1. Field of the Invention
This invention relates to a starter motor, more particularly to a starter motor usable as a power source for other than engine start.
2. Related Art Statement
A starter motor for carrying out the engine start has heretofore been provided for the specialized functional purpose. Accordingly, the starter motor has been useless except when it is engaged in the engine start, because it is totally out of operation at other times. As shown in Japanese Patent Laid-Open No. 56-6065 or Japanese Utility Model Laid-Open No. 56-165988 for example, power to the outside is taken out from a transmission system of the starter motor.
However, these starter motors are each constructed such that the engine start is carried out at one side of the output shaft and the power is taken out to the outside at the other side of the output shaft, thereby presenting such a disadvantage that the provision of seal construction between the output shaft and a case is necessary at two positions thus increasing the possibility of seal failure.
Then, when two outputs including an output for the engine start and another output for the power to the outside are taken out on one side of the output shaft, the seal construction can be favorably simplified. However, with this arrangement, to bear thrusts from the respective output shafts in the axial directions thereof, new countermeasures must be taken with a view to reducing the number of parts and improving structural integrity.
It is preferable that lubrication for the high speed rotation be applied to members positioned close to the motor and lubrication for the high load be applied to speed-reduced members. However, in the case of the above-described conventional technique, it is extremely difficult to form lubricating means to overcome the problems, so that the above-described conventional technique cannot be adopted immediately.
Furthermore, a known starter motor for carrying out the engine start, as shown in Japanese Patent Laid-Open No. 60-173366 for example, includes a speed reduction mechanism having planetary gears in a power transmission system extending from a motor shaft to the output shaft provided thereon with a pinion gear. In this case, locking against fall-off of the planetary gears from the pin shafts is carried out by stopper provided on the side of a sun gear.
However, the locking against fall-off by the stopper is carried out on the side of the inner periphery of an orbital motion of the planetary gears, i.e. on the side of the sun gear, whereby a scope is small in which the stopper is abutted against the side surfaces of the planetary gears to carry out the substantial locking against fall-off. Moreover, as the stopper is provided on the side of the sun gear, with which the planetary gears are in meshing engagement and the power is transmitted therebetween, the planetary gears cannot satisfactorily be locked against fall-off, thus presenting such a problem that, when a heavy load acts on the planetary gears at the time of the engine start, the planetary gears become eccentric and smooth power transmission can not be effected.
Further, when a planetary gear mechanism is used as a speed reduction section, on an output shaft from the planetary gear mechanism, there are integrally formed a large diameter flanged portion for rotatably supporting the planetary gears and a small diameter gear portion on the output side.
However, according to the conventional forming process by the cold forging, there has not been known such a process that the above-described pinion shaft provided at one end thereof with the small diameter gear portion and at the other end with the large diameter flanged portion is formed by a series of forging steps, because the gear portion cannot be effectively protected. As a result the pinion shaft is formed through a time consuming process such as cutting, thus presenting such problems that the efficiency is low, and moreover, the cost is disadvantageously high.